1. Field of the Invention
The present invention relates to a treatment apparatus and a treatment method for treating a gas containing organic substances used as organic solvents and the like by using an adsorbent. More particularly, the present invention relates to a technique of adsorbing in an adsorbent the organic substances used as organic solvents such as trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, and the like and contained in the gas to be treated and then decomposing the organic solvents. The present invention can be preferably employed for treating organic solvents and the like polluting the environments such as soil, groundwater, and the like by gasifying the solvents or for treating a waste gas containing organic solvents and the like from a factory.
2. Related Background Art
Conventionally, an organic solvent-containing gas treatment apparatus using an adsorbent in a common manner has been employed to recover volatile organic solvents such as trichloroethylene, 1,1,1-trichloroethane, tetrachloroethylene, cis-1,2-dichloroethylene and Freons, by bringing a gas to be treated into contact with a porous adsorbent such as an activated carbon to adsorb and collect these solvents and then desorbing the adsorbed substances from the activated carbon by heating with steam or the like.
Such a system is composed of an activated carbon tower, a condenser to be connected to the discharge side of the activated carbon tower, a decanter, and an aeration tank to be connected to the drain side of the decanter. The organic solvents adsorbed in the activated carbon are desorbed from the activated carbon by bringing steam for activated carbon regeneration into contact with the activated carbon and incorporated into the steam, and then the steam is introduced into the condenser together with the solvents. The condenser is set to a temperature from 10 to 30xc2x0 C. and liquefies the steam for regeneration discharged out of the activated carbon tower and then the resulting organic solvents and water are separated by gravity separation by the decanter. After that, further downstream, gaseous components and waste water are separated in the aeration tank and the resultant waste water is discharged outside to complete the treatment.
However, the foregoing conventional method possibly has the following problems:
(1) in some cases, a part of the recovered organic solvents is dissolved in waste water making it necessary to carry out further waste water treatment;
(2) in case of water-soluble organic solvents, recovery of organic solvents is sometimes difficult;
(3) if the organic solvents recovered by the decanter are reusable as they are, there is no problem. However, if they cannot be readily reused, they need to be treated to be reused or decomposed. If an incineration method is employed for the decomposition, there is a risk of causing further pollution such as dioxin generation; and
(4) polluting substances are discharged outside after separation of gaseous components and waste water in the aeration tank.
Hence, an object of the present invention is to provide a treatment apparatus and a treatment method for a substance to be decomposed not only which are capable of moving organic compounds such as organic solvents between media, but also which are useful for basically decomposing and eliminating the organic compounds without causing any waste water treatment problems.
Another object of the present invention is to provide an apparatus for treating a gas containing a substance to be decomposed, comprising adsorption means equipped with an adsorbent for adsorbing the substance to be decomposed, steam introduction means for bringing steam into contact with the adsorbent, condensation means for obtaining a condensed liquid containing the substance to be decomposed from the steam containing the substance, a reaction tank, condensed liquid supply means for supplying the condensed liquid to the reaction tank, hypochlorous acid supply means for supplying a solution containing hypochlorous acid to the reaction tank, and light irradiation means for irradiating the inside of the reaction tank with light.
Still, another object of the present invention is to provide a method for treating a gas containing a substance to be decomposed, comprising the steps of: (A) adsorbing the substance to be decomposed in an adsorbent by bringing a gas containing the substance to be decomposed into contact with the adsorbent, (B) shifting the substance to be decomposed to steam by bringing steam into contact with the adsorbent in which the substance to be decomposed is adsorbed, (C) obtaining a condensed liquid by condensing the steam containing the substance to be decomposed, (D) introducing the condensed liquid into a reaction tank and mixing the condensed liquid with a solution containing hypochlorous acid, and (E) decomposing the substance contained in the condensed liquid by irradiating the inside of the reaction tank with light.
The apparatus and the method of the present invention make it possible not only to move organic solvents between media, but also to basically decompose and eliminate pollutants from soil without causing any waste water treatment problems.